The present invention relates to a system for creating an image within an object.
Goldfarb, U.S. Pat. No. 5,575,936, discloses a system for etching an image within a solid article that includes the steps of focusing a laser to a focal point within the article and positioning the article with respect to the focal point. The laser is then fired so that a local disruption occurs within the article. The process is repeated to form the image within the article. Each local disruption creates a small localized but visible fracture., e.g. a three dimensional pixel. These pixels are combined together to create a three-dimensional (or two-dimensional) object inside the optical material. The pixels appear generally opaque because they scatter the light incident therein. In room light or sunlight they look white. In colored light they appear to be the same color as the light incident thereon. It is likewise generally known that a smaller amount of power will create a smaller local disruption while a larger amount of power will create a larger local disruption. However, the resulting size of the disruption is not easily controlled because the resulting catastrophic optical damage is not readily controllable. Unfortunately, the system taught by Goldfarb results in poor results when used with irregular shaped objects or spherical objects. In addition, the time it takes to etch an image is limited by the speed of the positioning system to position the article at the desired location, stop the positioning system, fire the laser to create the local disruption, and then reposition the positioning system at the next desired location. With thousands of pixels (local disruptions) necessary for many images it takes considerable time to create each finished article.
What is desired, therefore, is a system that may be used to create a set of dislocations within an object in a quick manner with high image quality.